Pediatric cancers of neural ectodermal origin are the most common solid tumor in children and are now the most common cause of cancer-related death in children. The goal of this grant is to define drugable targets for two of the most common pediatric cancers of the central nervous system - malignant medulloblastoma and low-grade astrocytoma. Neither of these tumors exhibits gross chromosomal instability that characterizes malignant astrocytomas in adults. Both tumors are generally wild type for the tumor suppressor genes most commonly mutated in adult CNS cancers - p53, RB and PTEN. On the other hand, upregulated kinase activity has been associated with poor outcome or increased metastatic potential in these tumors. The hypothesis of this grant is that the malignant phenotype for medulloblastoma and also for low-grade astrocytoma reflects a gain-of-function mutation within a single protein kinase (or a small number of kinases) unique to each tumor type. Recent insights into the genetics of malignant melanoma suggest that this hypothesis is reasonable. We have assembled a tripartite team in 1) Pediatric Oncology/Neuro Pathology, 2) Molecular Biology/Bioinformatics and 3) Signal Transduction/Drug Discovery that makes the hypothesis testable and our goal achievable. Our study plan has three aims: (1) to isolate DNA for mutation analysis from at least 15 medulloblastoma and 15 low-grade astrocytomas a year for three years. (2) to identify mutations in all tyrosine kinases and all serine/threonine and lipid kinases involved in oncogenic signaling pathways. Towards this end, we will sequence roughly 4000 exons, covering the entire coding sequences of tyrosine kinases and of all oncogenic serine/threonine kinases as well as key portions of the remaining serine/threonine kinases and type 1 PI3 kinases, (3) to characterize the biochemical activity and biological activity of the mutant kinases. Mutant kinases will be subjected to a battery of analytical tests to see if the mutation increases the specific activity of the kinase in vitro or in cells. Finally, we will determine if the mutation increases the transformation potential of the kinase. The research will lead to a new generation of selective therapeutics for children with brain cancer. Since cancers of children are often "informative" in a larger context, it is likely that these medicines will find use for more frequent adult cancers.